Soil Emissions Of CO2 Research Articles

Emissions intensity and carbon stocks of a tropical Ultisol after amendment with Tithonia green manure, urea and biochar

Biochar has been shown to reduce soil emissions of CO2, CH4 and N2O in short-term incubation and greenhouse experiments. Such controlled experiments failed to represent variable field conditions, and rarely included crop growth feedback. The objective of this study was to assess the effect of biochar, in comparison to green manure and mineral nitrogen, on greenhouse gas Emissions Intensity (EI=emissions in CO2 equivalents per ton of grain yield) in a low-fertility tropical Ultisol. Using a field trial in western Kenya, biochar (0 and 2.5tha−1; made from Eucalyptus wood) was integrated with urea (0 and 120kgNha−1) and green manure (Tithonia diversifolia; 0, 2.5 and 5tha−1) in a factorial design for four consecutive seasons from October 2012 to August 2014. Compared to the control, biochar increased soil CO2 emissions (9–33%), reduced soil CH4 uptake (7–59%) and reduced soil N2O emissions (1–42%) in each season, with no seasonal differences. N2O emissions increased following amendment with T. diversifolia (6%) and urea (13%) compared to the control. Generally, N2O emissions decreased where only biochar was applied. The greatest decrease in N2O (42%) occurred where all three amendments were applied compared to when they were added separately. EI in response to any of the amendments was lower than the control, ranging from 9 to 65% (33.0±3.2=mean±SE). The amendments increased SOC stocks by 0.1–1.2tha−1year−1 (mean±SE of 0.8±0.09tha−1year−1). The results suggest decreased net EI with biochar in low fertility soils mainly through greater net primary productivity (89% of the decrease).

CO2 soil emission under different methods of oil palm replanting

Colombian oil palm plantations have started a large-scale replanting phase. The replanting process has an effect on the disposal of biomass, plant health management, and agro-ecological conditions due to the disturbance that is generated. This document addresses soil respiration (CO2 flux) as a response variable of crop replanting. Seven renovation methods used in Colombia were tested. The measurements were taken over time after the disturbance and planting of the new crop. This study was carried out in the municipality of Tumaco between August of 2009 and June of 2011 using 7 methods of renovation and 4 stages of crop development. The CO2 flow was measured at 12 points in each plot. There were no significant differences for the CO2 emission among the replanting methods. The average value for respiration was 929 mg CO2 m-2 h-1 (± 270.3); however, significant differences were found over time. This response was not related to fluctuations of soil temperature and moisture; therefore, there should be an associated response to biotic factors (microbial organisms) not established in this study. The values suggested that the soil of the plots under a replanting process emitted considerable quantities of carbon into the atmosphere, but the emissions declined over time and, in turn, were offset by the photosynthesis of the new crop (14 μ CO2 m-2s-1 ± 1.4, data not shown), creating an overall positive carbon balance.

Effect of Hydrothermally Carbonized Hemp Dust on the Soil Emissions of CO2 and N2O

The impact on carbon dioxide (CO2) and nitrous oxide (N2O) emissions when applying hydrothermally carbonized (HTC) char to soil was investigated in a laboratory experiment with two HTC chars made from hemp (Cannabis sativa L.) dust and incubated for 131 d. Two fractions of hemp dust were collected during fiber processing (from fractionation and suction) and were carbonized at 230 °C for 6 h in water. Non-treated and water-washed HTC chars were used in incubation experiments, doubling the carbon concentration of the soil. As a result of adding HTC char to soil, CO2 emissions increased significantly in all cases compared to the control treatment. Washing the HTC chars easily removed dissolvable carbon (C) compounds, which significantly decreased CO2 emissions. Nitrous oxide emissions, following the incorporation of HTC char, did not differ from those of the control sample; however, washed HTC char treatments tended to emit less N2O than the corresponding unwashed samples. Hydrothermally carbonized char obtained from the suction of dust may play a greater role as a soil conditioner than HTC char from dust by fractionation because dust from suction accumulates to a larger degree during hemp fiber processing.

Dynamics of soil respiration at different stages of pyrogenic restoration succession with different-aged burns in Evenkia as an example

An analysis of CO2 emissions and soil microbiological activity has been performed in larch stands of different ages that developed on cryogenic soils and represent different stages of post-fire succession. An abrupt increase in the soil emissions of CO2 (by more than 2 times) in young stands (15–30 years old), as well as a decrease of soil-respiration rate at the later stages of pyrogenic successions because of the restoration of the moss-lichen cover and the closure of the stand canopy was seen. Intraseasonal and interannual variations of soil CO2 fluxes were also revealed; however, their dynamics was largely determined by the local conditions.

NO, N2O and CO2 soil emissions from Venezuelan corn fields under tillage and no-tillage agriculture

The largest share of Latin American and Caribbean (LAC) anthropogenic greenhouse gases is derived from land use changes as well as forestry and agriculture, representing up to 67 % of the relative contribution from all sources. However, in spite of the rapid expansion of LAC tropical agriculture, little is known about its impact on atmospheric trace gases emissions, such as nitrogen oxides (NO x ), nitrous oxide (N2O) and carbon dioxide (CO2), which are produced in soils by microbial processes and also accelerated in tropical climates. This information is crucial for assessing mitigation strategies linked to agricultural practices to satisfy food demands for the region’s future. We measured NO, N2O and CO2 soil emissions along with soil variables from corn fields under tillage (T) and no-tillage (NT) agriculture at two of the largest cereal-producing regions in Venezuela during the crop-growing season. We found statistically significant positive correlations between the logarithms of nitrogen gas emissions and soil inorganic nitrogen concentrations, soil water and clay contents. Average emissions of NO and CO2 were larger in T than NT sites, while N2O fluxes showed the opposite. CO2 emissions from T were 1.6 as much as those found in NT, whereas N2O was 0.5 of that found in NT. These results imply that NT practices more effectively mitigate climate change from these monoculture systems mainly because of CO2 emission reduction. We suggest then that agricultural mitigation actions for tropical monoculture systems should aim for the enhancement of NT management practices along with N fertilization rate reduction to compensate for the larger N2O emissions.

Soil Greenhouse Gas Emissions in Response to Corn Stover Removal and Tillage Management Across the US Corn Belt

In-field measurements of direct soil greenhouse gas (GHG) emissions provide critical data for quantifying the net energy efficiency and economic feasibility of crop residue-based bioenergy production systems. A major challenge to such assessments has been the paucity of field studies addressing the effects of crop residue removal and associated best practices for soil management (i.e., conservation tillage) on soil emissions of carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). This regional survey summarizes soil GHG emissions from nine maize production systems evaluating different levels of corn stover removal under conventional or conservation tillage management across the US Corn Belt. Cumulative growing season soil emissions of CO2, N2O, and/or CH4 were measured for 2–5 years (2008–2012) at these various sites using a standardized static vented chamber technique as part of the USDA-ARS’s Resilient Economic Agricultural Practices (REAP) regional partnership. Cumulative soil GHG emissions during the growing season varied widely across sites, by management, and by year. Overall, corn stover removal decreased soil total CO2 and N2O emissions by -4 and -7 %, respectively, relative to no removal. No management treatments affected soil CH4 fluxes. When aggregated to total GHG emissions (Mg CO2 eq ha−1) across all sites and years, corn stover removal decreased growing season soil emissions by −5 ± 1 % (mean ± se) and ranged from -36 % to 54 % (n = 50). Lower GHG emissions in stover removal treatments were attributed to decreased C and N inputs into soils, as well as possible microclimatic differences associated with changes in soil cover. High levels of spatial and temporal variabilities in direct GHG emissions highlighted the importance of site-specific management and environmental conditions on the dynamics of GHG emissions from agricultural soils.

Effect of organic-complexed superphosphates on microbial biomass and microbial activity of soil

Organic complexed super-phosphates (CSPs) are formed by the complexation of humic acid (HA) with calcium monophosphate. The aim of this study was to determine whether two CSPs, characterized by different HA concentrations, added to a calcareous soil at an agronomic dose, were able to maintain the phosphorus (P) in a soluble form longer than the superphosphate fertilizer. Another important goal was to verify if CSP could positively influence soil microbial biomass and soil microbiological activities. Organic complexed super-phosphates were capable of keeping a large portion of P in a soluble form under different soil water conditions. In particular, the CSP with the highest organic C content was the most effective product, capable of maintaining, in an available form, the 73 % of the initially added P at the end of the experiment. In addition, it was the most effective in increasing C–CO2 soil emission, microbial biomass carbon (C) and nitrogen (N), fluoresceine diacetate hydrolysis and activities of alkaline phosphomonoesterase, β-glucosidase and urease. The addition of CSPs to soil probably produced a priming effect, increasing several times C–CO2 release by the treated soil. The significant correlation (p < 0.05) between C–CO2 emission and the amount of C added to soil by CSP suggests that the added HA acted as trigger molecules.

Soil management affects carbon dynamics and yield in a Mediterranean peach orchard

A field trial was conducted over a seven-year period, in Mediterranean peach orchard. The aims were (i) to explore the effects of alternative soil-management practices (Amng) on soil and litter carbon (C) reserves, (ii) to monitor the seasonal and (iii) spatial variations of soil CO2 flushes. The alternative management included no tillage, retention of all aboveground biomass and application of imported organic amendments (15tha−1y−1 fresh weigh). Locally conventional management (Lmng) served as the control: i.e. tillage, mineral fertilisation, removal of prunings. The mean total annual C inputs were 4.2 and 2.4tha−1 in Amng and Lmng, respectively. Spatial and temporal variations in CO2 soil emissions over a 20m2 plot (×2) were assessed (Li-6400, LI-COR, USA) on the assumption that root topography and microbial activity declined systematically with distance from the row line. Under Amng practices soil C significantly increased up to 1.78% against 1.38% at Lmng block. The C stored as litter and dead wood in Amng, was 16-times that in Lmng. On a whole-season basis, CO2 losses were 20% higher in Amng than in Lmng. Soil CO2 emissions were mostly from the in-row, with the inter-row emissions being lower, especially due to reduced soil-water content during the drier months. It is concluded that despite a higher CO2 soil emissions, alternative management techniques will partially offset atmospheric CO2 rise through increased soil C reserves, and that spatial variability of emissions must be taken into account if the accuracy of estimates of large-scale emissions are to be improved.

A cross‐ecosystem assessment of the effects of land cover and land use on soil emission of selected greenhouse gases and related soil properties in Zimbabwe

Land used for agricultural production can contribute significantly to greenhouse gas (GHG) emissions; however, there is very little information on the role of management and land use change in influencing these emissions in Africa. Thus, exploring GHG emissions that occur at the soil‐atmosphere interface is an essential part of the effort to integrate land management strategies with climate change mitigation and adaptation in southern Africa. We measured soil emissions of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) from rain‐fed perennial tropical grassland, wastewater‐irrigated perennial tropical pastureland, recently cleared woodland, miombo woodland, a Eucalyptus plantation, regular cropland and recently cleared‐and‐cropped land, on two contrasting soils at five sites in one cropping season in Zimbabwe. Gas samples were collected using static chambers and analysed by gas chromatography. Considerably high GHG emissions were found on sewage effluent‐irrigated pastureland (means, 190 mg CO2‐C m−2 hour−1, 102 µg CH4‐C m−2 hour−1 and 6 µg N2O‐N m−2 hour−1 from sandy soil) and altered woodlands (mean ranges, 38–70 CO2‐C m−2 hour−1, 12–43 µg CH4‐C m−2 hour−1 and 20–31 µg N2O‐N m−2 hour−1 from deforested and cultivated woodland on clay and sandy soils). Relatively low and less variable emissions were found among the rain‐fed perennial tropical grasslands, regular croplands and Eucalyptus plantations (mean ranges, 19–39 mg CO2‐C m−2 hour−1, −9.4–2.6 µg CH4‐C m−2 hour−1 and 1.0–4.7 µg N2O‐N m−2 hour−1). Variability in CO2, CH4 and N2O emissions from soils was to the greatest extent influenced by soil temperature, but soil moisture, mineral‐N and pH were also important. The increased N2O emissions from cleared woodland on clay soil were attributed to increased mineralization and N availability when no tree could take up that N, while the N mineralized on the sandy soil could have been largely leached due to the soil's poor nutrient holding capacity, resulting in a relatively lower N2O emission response to clearing. We concluded that the alteration of woodlands by deforestation and cultivation increased soil temperature, resulting in increased soil respiration, while the establishment of Eucalyptus plantations may provide an option for reduction in soil emissions of CO2 and N2O and a sink for CH4.

Rotação de culturas no sistema plantio direto em Tibagi (PR): II - Emissões de CO2 e N2O

A atividade agrícola pode alterar a quantidade e qualidade da matéria orgânica do solo (MOS), resultando em emissões de dióxido de carbono (CO2) e óxido nitroso (N2O) do solo para a atmosfera. O sistema plantio direto (SPD) com a utilização de leguminosas em sistemas de rotação é uma estratégia que deve ser considerada tanto para o aumento da quantidade de MOS como para seu efeito na redução das emissões dos gases de efeito estufa. Com o objetivo de determinar os fluxos de gases do efeito estufa (CO2 e N2O) do solo, um experimento foi instalado em Tibagi (PR), em um Latossolo Vermelho distroférrico textura argilosa. Os tratamentos, dispostos em faixas não casualizadas com parcelas subdivididas, foram: sistema plantio direto por 12 anos com sucessões milho/trigo e soja/trigo (PD12 M/T e PD12 S/T, respectivamente) e por 22 anos (PD22 M/T e PD22 S/T, respectivamente). As emissões de CO2 do solo foram aproximadamente 20 % mais elevadas no PD22 em relação ao PD12. As emissões de CO2 apresentaram correlação significativa (R² = 0,85; p &lt; 0,05) com a temperatura do solo, com emissões médias 40 % menores, registradas nos meses com temperaturas mais baixas. As emissões mais elevadas de N2O foram observadas após a colheita das culturas de verão, sobretudo na sucessão milho/trigo, em relação à sucessão soja/trigo. As emissões de N2O foram aproximadamente 25 % maiores após aplicação do fertilizante nitrogenado na cultura do trigo nas duas sucessões e apresentaram correlação significativa (R² = 0,88; p &lt; 0,01) com o grau de saturação de água no solo (Sr %).

SOIL FLUXES OF CO2, CO, NO, AND N2O FROM AN OLD PASTURE AND FROM NATIVE SAVANNA IN BRAZIL

We compared fluxes of CO2, CO, NO, and N2O, soil microbial biomass, and N availability in a 20‐yr‐old Brachiaria pasture and a native cerrado area (savanna in central Brazil). Availability of N and NO fluxes were lower in the pasture than in the cerrado. N2O fluxes were below detection limit at both sites. The CO fluxes showed weak seasonal variation with slightly higher positive fluxes in the dry season and lower fluxes, including net consumption, during the wet season. The cerrado CO fluxes were higher and more variable than the fluxes in the pasture. Both sites showed a seasonal pattern in CO2 emissions with lower fluxes (∼2 μmol CO2·m−2·s−1) during the dry season. There were no significant differences in annual CO2 soil emissions between the cerrado and the pasture, but the temporal trends differed, with higher fluxes in the pasture during the transition from the wet to the dry season. Artificial water addition in the pasture during the dry season resulted in short‐lived pulses of NO and CO2.

Unexpected results of a pilot throughfall exclusion experiment on soil emissions of CO 2 , CH 4 , N 2 O, and NO in eastern Amazonia

The eastern Amazon Basin may become drier as a result of less regional recirculation of water in a largely deforested landscape and because of increased frequency and intensity of El Nino events induced by global warming. Drier conditions may affect several plant and soil microbial processes, including soil emissions of CO2, CH4, NO, and N2O. We report here unanticipated results of a pilot study that was initiated to test the feasibility of a larger-scale throughfall exclusion experiment. In particular, soil drying caused a switch from net consumption of atmospheric CH4 by soils in the control plot to net CH4 emission from soils in the experimentally dried plot. This result is surprising because production of CH4 requires anaerobic microsites, which are uncommon in dry soil. A plausible explanation for increased CH4 emissions in the dried plot is that dry soil conditions favor termite activity and increased coarse root mortality provides them with a substrate. Another surprise was that both NO and N2O fluxes were elevated several years after initiation of the drying experiment. Apparently, a pulse of N availability caused by experimental drying persisted for at least 3 years. As expected, CO2 emissions were lower in the dried plots, which is consistent with lower rates of root growth observed in root in-growth cores placed in the dried plots. More work is needed to test these explanations and to confirm these phenomena, but these results demonstrate that changes in climate could have unanticipated effects on biogeochemical processes in soils that we do not adequately understand.